Remove Faraday

We've just removed the only code in the app that used this.

It was only being used for sending EventLogs to Splunk. Or at least, by
the code that was intended to send EventLogs to Splunk, but hadn't sent
any for a few years.

Gemfile

@@ -14,7 +14,6 @@ gem "devise-encryptable"
 gem "devise_invitable"
 gem "devise_zxcvbn", "~> 1.1"
 gem "doorkeeper"
-gem "faraday"
 gem "json"
 gem "kaminari"
 gem "kubeclient"

Gemfile.lock

@@ -77,7 +77,6 @@ GEM
     ast (2.4.2)
     autoprefixer-rails (10.4.7.0)
       execjs (~> 2)
-    base64 (0.1.1)
     bcrypt (3.1.18)
     better_errors (2.10.1)
       erubi (>= 1.0.0)
@@ -147,11 +146,6 @@ GEM
     factory_bot_rails (6.2.0)
       factory_bot (~> 6.2.0)
       railties (>= 5.0.0)
-    faraday (2.7.11)
-      base64
-      faraday-net_http (>= 2.0, < 3.1)
-      ruby2_keywords (>= 0.0.4)
-    faraday-net_http (3.0.2)
     ffi (1.15.5)
     ffi-compiler (1.0.1)
       ffi (>= 1.0.0)
@@ -731,7 +725,6 @@ DEPENDENCIES
   devise_zxcvbn (~> 1.1)
   doorkeeper
   factory_bot_rails
-  faraday
   gds-api-adapters
   govuk_admin_template
   govuk_app_config